Since no-one has mentioned Karajan's Sibelius recordings (as far as I noticed in a quick skim through the replies), I will. His DG LP of the fifth was a key item for me, I bought a mono copy in WH Smiths on Waterloo Station for a few shillings back in the late sixties. The fact that it was mono was not a drawback, because I only had one speaker at the time (being a poor student), and it was a great time to discover music, because all the stores were selling off their residual mono stock dirt cheap, before everyone converted to stereo and the mono items were unsaleable. Later, when I could afford two speakers, I bought the stereo and I still have it. Just glorious, the final ride to the last timpani blows has an irresistible force. Sibelius needs no support from me, he is a great composer and Karajan can show us how great he was.
And the companion records of the sixth/seventh and fourth are pretty wonderful, too.
I'm not sure about his earlier mono recording of the fourth for Columbia (33CX 1125), but I expect its very fine. But its a long time since I played it and there are too many recordings out there to finnick around comparing them, I need to get on and play some new items.